I did have problems though, it reported that it couldn't continue with the install as I had "broken packages". I was able to fix these by running Synaptic Package Manager , filtering out just the broken ones and then right-clicking on them and choosing "reinstall". After a quick reboot I then re-ran the Update Manager which continued the install.

It does take quite a long time to perform the upgrade, mine was still downloading the required packages after two hours but I now have a fully working Ubunutu with Firefox 2.0! :)